1. Field of the Invention
The invention provides devices and methods for casing a drilled bore. In particular aspects, the invention relates to wellbore casings that are formed using expandable tubing.
2. Description of the Related Art
Following drilling, a wellbore is typically lined with a casing in order to prevent the borehole from collapsing and to prevent undesirable fluid migration through the borehole wall. Often, a wellbore is drilled in successively deeper intervals. As a result, the lower intervals are cased with strings of casing having successively smaller diameters. Since the casing sections for the lower intervals must be able to pass through the interior diameter of the upper intervals. This places significant size limitations on the wellbore at significant depths.
Recently, processes have been developed for the use of casing members that are radially plastically-expandable. This permits the lower intervals of the wellbore to have the same diameter as the casing sections above. An example of such systems is the LinEXX system, which is available commercially from Baker Hughes Incorporated in Houston, Tex. The lower casing member is disposed through the upper casing member in a radially collapsed state. Then, an expansion member, such as a swage, is used to expand the lower casing member radially. Thereafter, the lower casing member may be cemented into place within the wellbore. Alternatively, open hole packers can be utilized on the exterior of the expanded tubular to perform the required zonal isolation functionality. In addition, the lower casing member must be joined to the upper casing member so that a continuous lining of the borehole is created. Ordinarily, this is done by forming an expanded diameter upset, or recess, in the lower end of the upper casing member. Then the upper end of the lower casing member is located within the recess.
In expandable casing systems, the ability to locate the lower casing member with respect to the upper casing member within the wellbore is critical to proper construction of the casing string. FIG. 1 illustrates a situation wherein the upper end 10 of the lower casing member 12 is too high within the wellbore with respect to the upper casing member 14. As a result, the upper end 10 of the lower casing member 12 lies above the recess 16 that has been formed in the upper casing member 14. Upon expansion of the lower casing member 12, the upper end 10 will not be fully expanded due to the restriction provided by the upper casing member 14. This results in a restricted diameter blockage 18 within the casing string.
FIG. 2 depicts an alternative situation in which the upper and lower casing members 14, 12 are improperly located with respect to each other. In this instance, the lower casing member 12 is located too far below the upper casing member 14. As a result, the upper end 10 of the lower casing member 12 does not reside within the recess 16, and there is an undesirable break in the string of casing.
In prior art systems, the recess is formed in the upper casing member in a separate step before the lower casing member is run-in and expanded. The recess is typically formed using a rotary expansion tool. At the same time that the recess is formed, a locating profile may be formed into the upper casing member as well.
A significant problem associated with many contemporary expandable casing systems is that an extra trip into the wellbore is needed to create the recess in the upper casing member following the primary diametrical expansion of the upper casing member. This entails significant time and cost. In addition, conventional locating devices are not generally sufficient to locate a lower casing member with respect to an upper casing member. Existing methods are limited (e.g., run to bottom of hole, then space out from bottom or run below the shoe then space out from the bottom of the shoe) and all require running deeper than necessary. Furthermore, conventional methods are problematic with regard to getting stuck on bottom or getting stuck pulling back from an open hole into a cased hole.